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Humans in the Biosphere

Chapter 6

Section 6-1

A Changing Landscape

2

Earth as an Island

Earth is similar to an island because all the

organisms that live on Earth share a

limited resource base and depend on it for

their long-term survival.

3

Human Activities

• Humans participate in food webs and

chemical cycles which provide:

– breathable air

– drinkable water

– fertile soil

• Ecosystem processes provide us with

"services" such as storage and recycling of

nutrients.

• If we don't get these "goods and services"

from the environment, we will need to

spend money to produce them.

4

Hunting and Gathering

• Way our ancestors obtained food.

• Caused mass extinction of animals in North

America about 12,000 years ago.

• Groups of people still practice this method

today:

– Bushmen in Africa

– Pygmies

– Eskimos

• Most use technology such as guns,

snowmobiles, or manufactured tools.

5

Agriculture

• About 11,000 years ago, humans began

the practice of farming, or agriculture.

• Also included raising animals.

• One of the most important developments

in human history.

• Provides a dependable food supply that

can be produced in large quantities and

stored for later use.

• Lead to large settlements and stable

communities.

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From Traditional to Modern

Agriculture

• Machinery helped farmers with

cultivation.

• World exploration led to an exchange of

crops around the globe.

• Large scale irrigation in dry areas

appeared in the Western US allowing

deserts to become breadbaskets

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• New varieties of crops were developed to

produce higher yields.

• These crops were grown using

monoculture in which large fields are

planted with a single variety year after year.

• Chemical fertilizers boosted plant growth

and pesticides controlled crop-damaging

insects.

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The Green Revolution

• The green revolution greatly increased the

world's food supply.

• Plant breeder's developed highly

productive "miracle strains" of wheat and

rice.

• Modern techniques were introduced to

countries that were suffering from food

shortages.

• Helped the world food production double.

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Challenges for the Future

• Modern agriculture has created ecological

challenges.

– Increased use of pesticides which:

• contaminate water

• damage beneficial insects

• accumulate in the environment

– Finding enough water for irrigation

• Ogallala aquifer in Midwest expected to run dry

within 20 to 40 years.

• Need for developing new approaches to

protect natural resources

10

Industrial Growth and Urban

Development• Industrial Revolution transformed human

society.

• Mass-produced farm machinery makes

efficient, large-scale agriculture possible.

• Energy produced from fossil fuels pollutes

the air, water, and soil.

• Dense communities produce wastes.

• Suburban growth consumes farmland and

natural habitats.

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Renewable and

Nonrenewable

Resources

Section 6-2

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Classifying Resources

• Environmental goods and services may be

classified as either renewable or

nonrenewable.

• A renewable resource can regenerate if it

is alive, or can be replenished by

biochemical cycles if they are nonliving.

– A tree because a new tree can grow in place of

an old tree.

• A renewable resource is not necessarily

unlimited.

– Fresh water can easily become limited by

drought or overuse.

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•A nonrenewable resource is one

that cannot be replenished by

natural processes.

–Fossil fuels - coal, oil, and natural gas

are nonrenewable resources. When

they are depleted, they are gone

forever.

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Sustainable Development

• Sustainable development is a way of using

natural resources without depleting them,

and providing for human needs without

causing long-term environmental harm.

• Human activities can affect the quality

and supply of renewable resources such

as:

•land

•forest

•fisheries

•air

•fresh water

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Land Resources

• Land is a resource that provides space for

human communities and raw materials for

industry.

• Land also includes the soils in which crops

are grown.

• The most fertile soil is in the uppermost

layer called topsoil.

• Plowing the land can break up the soil

• Soil erosion is the wearing away of surface

soil by water and wind.

– The Midwest loses roughly 47 metric tons of

topsoil/hectare every year!

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• In dry climates, a combination of farming,

overgrazing, and drought has turned once

productive areas into deserts a process

called desertification.

• Some sustainable-development practices

guard against these problems:

– Contour plowing - fields are plowed across the

slope to reduce erosion

– Leaving the stems and roots of the previous

year's crop in place

– Planting a field with rye rather than leaving it

unprotected from erosion.

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Forest Resources

•Forests have been called the "lungs of

the Earth" because they remove CO2

and produce O2.

•Forests provide:

–Wood for homes, paper, fuel

–Store nutrients

–Provide habitats and food for organisms

–Moderate climate

–Limit soil erosion

–Protect freshwater supplies

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•Worldwide, about half of the area

originally covered by forests and

woodlands has been cleared.

•Only about one-fifth of the world's

original old-growth forests remain.

•Deforestation or loss of forests can

lead to severe erosion as soil is

exposed to heavy rains.

•Grazing or plowing after

deforestation can change local soils

and microclimates that may prevent

regrowth of trees.

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• Sustainable-development strategies

for forest management:

–Mature trees are harvested selectively to

promote growth of younger trees

–Foresters plant, manage, harvest, and

replant tree farms.

–Tree geneticists are also breeding new,

faster-growing tree varieties that

produce high quality wood.

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Fishes and other animals that live in water are a valuable source of food for humanity.

Fishery Resources

21

Overfishing

• Overfishing, or harvesting fish faster than they can be replaced by reproduction, greatly reduced the amount of fish in parts of the world's ocean.

• From 1950-1990, the world fish catch grew from 19 million tons to more than 90 million tons.

• The declining fish populations are an example of the "tragedy ofcommons".

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• "Tragedy of commons" is when people from several countries take advantage of a resource but no one take responsibility for maintaining it.

• Sustainable-development strategies:– Guidelines were created by the U.S. National Marine Fisheries Service• specified how many fish, and of what size, could be caught in various parts of the oceans.

• regulations helped fish populations recover

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• Aquaculture is the raising of aquatic animals for human consumption.

• It also helps to sustain fish resources.

• If it is not managed properly, aquaculture can pollute water and damage aquatic ecosystems.

Aquaculture

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Air Resources

• Air is a resource that affects

people's health and it's quality

remains a challenge for modern

society.

• Smog is mixture of chemicals that

occurs as a gray-brown haze in the

atmosphere.

• Smog is due to automobile exhaust

and industrial emissions.

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• Smog is a pollutant.

• A pollutant is a harmful material that

can enter the biosphere through land,

air, or water.

• The burning of fossil fuels can

release pollutants into the

atmosphere.

• Toxic chemicals are nitrates, sulfates,

and particulates which are

microscopic particles of ash and

dust.

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• Factories control their emissions

from smokestacks.

• Strict automobile emission

standards and clean-air regulations

have greatly improved air quality in

the US.

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Emissions to Atmosphere

Nitrogen oxides

Sulfur dioxide

Chemical Transformation

Nitric acid

Sulfuric acid

Precipitation

Acid rain, fog,

snow, and mist

Dry Fallout

Condensation

particulates, gases

Industry Transportation Ore smelting Power generation

Formation of Acid Rain

Nitrogen and sulfur compounds when combinedwith water vapor forms acid rain.

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Freshwater Resources

• Americans use billions of liters of

freshwater daily for drinking and

washing to watering crops and making

steel.

• Pollution threatens water supplies in

several ways:

Improperly discarded chemicals in

streams and rivers

Waste on land can seep through soil and

enter groundwater

Domestic sewage (sinks and toilets)

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• Sustainable use of water is to protect

natural systems involved in the water

cycle.

Wetlands purify water passing through them.

Forests and other vegetation help to purify the

water that seeps into the ground.

• Water conservation is an important aspect

of sustainable development.

• More than three quarters of all water

consumed is used in agriculture.

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Biodiversity

Section 6-3

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The Value of Biodiversity

• Biodiversity is the sum total of the

genetically based variety of all organisms

in the biosphere.

• Ecosystem diversity includes the variety of

habitats, communities, and ecological

processes in the living world.

• Species diversity refers to the number of

different species in the biosphere.

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Insects

BacteriaFungi

Plants

Protists Other Animals

54.4%

4.2%

18%

3.4%0.3%

19.7%

Species Diversity

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• Genetic diversity refers to the sum total of

all the different forms of genetic

information carried by all organisms

living on Earth today.

• Biodiversity is one of Earth's greatest

natural resources providing us with:

• Foods

• Industrial products

• Medicines (antibiotics, heart drugs,

anticancer drugs, painkillers)

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Threats to Biodiversity• Human activity can reduce biodiversity by:

• altering habitats

• hunting species to extinction

• introducing toxic compounds into food webs

• introducing foreign species to new environments

• Altering ecosystems can lead to:

• Extinction - species disappears from all or part

of its range.

• Endangered species - a species whose

population size is declining in a way that places

it in danger of extinction.

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Habitat Alteration

• As habitats disappear, the species that live

in those habitats vanish.

• Habitat fragmentation occurs when

development often splits ecosystems into

pieces.

• The pieces of the habitat become biological

"islands".(habitat surrounded by different habitat)

• New York's Central Park is an island of trees

and grass in a sea of concrete.

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Demand for Wildlife Products

• Some animals species have been hunted to

extinction for food or other products.

• meat, fur, hides, horns, tusks

• Hunting threatens rare animals in Africa,

South America, and Southeast Asia.

• CITIES bans international trade in products

derived from a list of endangered species.

• Today, endangered species are protected

from hunting.

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Pollution

• DDT is a historical case of a pesticide

being passed through the food chain.

• Nonbiodegradable (cannot be broken down)

• Not eliminated form an organisms body

• Because it remains stored in an organisms

tissues, it has the ability to be passed

through the food chain.

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Fish-Eating Birds

Magnification of

DDT Concentration

10,000,000

100,000

10,000

1,000,000

1

1000

LargeFish

Small Fish

Zooplankton

Producers

Water

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• Biological magnification is a process where

concentrations of a harmful substance

increase in organisms at higher trophic levels

in a food chain or food web.

• DDT caused egg shells of osprey, brown

pelicans and eagles to thin threatening

survival.

• Banned in early 1970's in the U.S.

• Populations of endangered birds has

recovered.

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Introduced Species

• Apparently harmless plants and animals are

introduced into new habitats.

• Invasive species reproduce rapidly because

their new habitats lack predators that

control their population.

• Zebra mussels (Great Lakes)

• Cane toads (Australia)

• Leafy spurge (Northern Great Plains)

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Conserving Biodiversity

• Conservation is used to describe the wise

management of natural resources.

• The modern science of conservation

biology seeks to protect biodiversity.

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Strategies for Conservation

• Manage individual species to keep them

from becoming extinct.

• Zoos have captive breeding programs (ferrets)

• Protecting entire ecosystems

• Ensures that the natural habitat and many

species are preserved at the same time

• Parks and preserves

• Marine sanctuaries

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• "Hot spots" have been designated as a

priority location where significant numbers

of habitats and species are in immediate

danger.

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Conservation Challenges

• Protecting resources for the future can

require people to change the way they earn

their living today.

• Conservation efforts attempt to maximize

benefits while minimizing economic costs.

Charting a Course for the

Future

Section 6-4

Ozone Depletion

Ozone layer is 20-50 kilometers above the

Earth's surface.

Molecules of ozone consist of O3.

Ozone at ground level is a pollutant.

The ozone layer absorbs the harmful UV rays

from the sun.

Overexposure to UV rays causes:sunburncancerdamages eyesdecreases and organisms' resistance to disease

The ozone layer serves as a global sunscreen.

In 1970's scientists found a "hole" over

Antarctica during winter.

That hole has grown larger and a similar "hole"

has now appeared over the Arctic.

Gases called chloroflurocarbons, or CFCs

were found to damage the ozone layer.

CFCs were used in:

Aerosol cans

Coolant in refrigerators, freezers, and air conditioners

Production of plastic foams

In 1987, the U.S., and many nations

began reducing the use of CFCs.

Today, most uses of CFCs are banned.

Current data that the ozone holes should

shrink and disappear within 50 years.

http://www.theozonehole.com/1980 09/25/09

Global Climate Change

Since the late 19th century, average

temperatures on Earth's surface have risen about

0.6 Celsius degrees.

Since 1980, average temperatures have risen

between 0.2 and 0.3 Celsius degrees.

The 1990s were the warmest decade ever with

1998 the warmest since record keeping began.

Global warming is the increase in average

temperature of the biosphere.

One sign is melting of polar ice.

Evidence of Global Warming

Researchers must determine whether the

current warming trend is part of a larger,

natural cycle of climate change, or whether it

is caused by human activity.

The most widely accepted hypothesis is the

warming is related to human activities that

are adding carbon dioxide and other

greenhouse gases to the atmosphere faster

than the carbon cycle can remove it.

The atmosphere is now retaining more heat.

Possible Effects of Global

Warming

Average global surface temperatures will

increase 1 to 2 Celsius degrees by the year

2050.

Sea levels may rise enough to flood some coastal

areas.

Parts of North America may experience more

droughts during the summer growing season.

Long-term change in climate will affect

ecosystems and threaten the organisms that

live there.

The Value of a Healthy

Biosphere

The scientists concern with these changes is

due to the importance of the goods and

services we get from the environment.

Water purification to waste recycling

Pollination of many crop plants by insects

Reservoir of new medicines and new varieties of

crops

People must make wise choices in the use and

conservation of resources.